The ref_cats directory should contain ps1_pv3_3pi_20170110, not actually be it. See the template path the butler’s expecting. So the tree should be something like:
/path/to/repo/
|-- various/
|-- directories/
|-- ref_cats/
`-- ps1_pv3_3pi_20170110/
|-- config.py
|-- master_schema.fits
|-- README.txt
`-- <index>.fits